FinFET Devices and Methods of Forming

ABSTRACT

A finFET device and methods of forming a finFET device are provided. The method includes forming a capping layer over a fin of a fin field effect transistor (finFET), where the fin is formed of a material comprising germanium. The method also includes forming a dummy dielectric layer over the capping layer. The method also includes forming a dummy gate over the dummy dielectric layer. The method also includes removing the dummy gate.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. application Ser. No.15/641,042, filed Jul. 3, 2017, entitled “FinFET Devices and Methods ofForming,” now U.S. Pat. No. 10,164,066, issued Dec. 25, 2018, whichclaims priority to U.S. Provisional Application No. 62/427,332, filed onNov. 29, 2016, both of which are hereby incorporated by reference intheir entirety.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as, for example, personal computers, cell phones, digital cameras,and other electronic equipment. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductor layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry continues to improve the integration densityof various electronic components (e.g., transistors, diodes, resistors,capacitors, etc.) by continual reductions in minimum feature size, whichallow more components to be integrated into a given area. However, asthe minimum features sizes are reduced, additional problems arise thatshould be addressed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a perspective view of a fin field effect transistor (“finFET”)device in accordance with some embodiments.

FIGS. 2-5 are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 6A and 6B are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 7A and 7B are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 8A and 8B are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 9A and 9B are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 10A, 10B, and 10C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIGS. 11A, 11B, and 11C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIGS. 12A, 12B, and 12C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIGS. 13A, 13B, and 13C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIGS. 14A, 14B, and 14C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIGS. 15A, 15B and 15C are cross-sectional views of an intermediatestages in the manufacture of a finFET device in accordance with someembodiments.

FIGS. 16A, 16B, and 16C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIG. 17 is a cross-sectional view of an intermediate stage in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 18A, 18B and 18C are cross-sectional views of an intermediatestage in the manufacture of a finFET device in accordance with someembodiments.

FIGS. 19A, 19B, and 19C are cross-sectional views of intermediate stagesin the manufacture of a finFET device in accordance with someembodiments.

FIG. 20 is a cross-sectional view of an intermediate stage in themanufacture of a finFET device in accordance with some embodiments.

FIGS. 21A and 21B are cross-sectional views of intermediate stages inthe manufacture of a finFET device in accordance with some embodiments.

FIGS. 22A and 22B are cross-sectional views of intermediate stages inthe manufacture of a finFET device in accordance with some embodiments.

FIGS. 23A and 23B are cross-sectional views of intermediate stages inthe manufacture of a finFET device in accordance with some embodiments.

FIGS. 24A and 24B are cross-sectional views of intermediate stages inthe manufacture of a finFET device in accordance with some embodiments.

FIGS. 25A and 25B are cross-sectional views of intermediate stages inthe manufacture of a finFET device in accordance with some embodiments.

FIGS. 26 and 27 are cross-sectional views of intermediate stages in themanufacture of a finFET device in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 illustrates an example of a fin field-effect transistor (FinFET)30 in a three-dimensional view. The finFET 30 comprises a fin 36 on asubstrate 32. The finFET 30 also includes isolation regions 34 formedover the substrate 32, and the fin 36 protrudes above and from betweenneighboring isolation regions 34. A gate dielectric 38 is alongsidewalls and over a top surface of the fin 36, and a gate electrode 40is over the gate dielectric 38. Source/drain regions 42 and 44 aredisposed in opposite sides of the fin 36 with respect to the gatedielectric 38 and gate electrode 40. FIG. 1 further illustratesreference cross-sections that are used in later figures. Cross-sectionA-A is across a channel, gate dielectric 38, and gate electrode 40 ofthe FinFET 30. Cross-section C-C is in a plane that is parallel to crosssection A-A and is across fin 36 outside of the channel region.Cross-section B-B is perpendicular to cross-section A-A and is along alongitudinal axis of the fin 36 and in a direction of, for example, acurrent flow between the source/drain regions 42 and 44. Subsequentfigures refer to these reference cross-sections for clarity.

Some embodiments discussed herein are discussed in the context ofFinFETs formed using a gate-last process. In other embodiments, agate-first process may be used. Also, some embodiments contemplateaspects used in planar devices, such as planar FETs.

FIGS. 2 through 27 are cross-sectional views of intermediate stages inthe manufacturing of FinFETs in accordance with an exemplary embodiment.FIGS. 2 through 5, and 26 and 27, illustrate reference cross-section A-Aillustrated in FIG. 1, except for multiple FinFETs. In FIGS. 6A-Bthrough 25A-B, figures ending with an “A” designation are illustratedalong a similar cross-section A-A; figures ending with a “B” designationare illustrated along a similar cross-section B-B; and figures endingwith a “C” designation are illustrated along a similar cross-sectionC-C. FIGS. 17 and 20 are depicted along cross section C-C.

FIG. 2 illustrates a substrate 50 comprising bottom substrate 50A andepitaxy region 50B. Bottom substrate 50A may be a semiconductorsubstrate, such as a bulk semiconductor, a semiconductor-on-insulator(SOI) substrate, or the like, which may be doped (e.g., with a p-type oran n-type dopant) or undoped. The bottom substrate 50A may be a wafer,such as a silicon wafer. Generally, an SOI substrate comprises a layerof a semiconductor material formed on an insulator layer. The insulatorlayer may be, for example, a buried oxide (BOX) layer, a silicon oxidelayer, or the like. The insulator layer is provided on a substrate,typically a silicon or glass substrate. Other substrates, such as amulti-layered or gradient substrate may also be used. In someembodiments, the semiconductor material of the substrate 50 may includesilicon; germanium; a compound semiconductor including silicon carbide,gallium arsenic, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP,AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof.

Epitaxy region 50B may be formed over bottom substrate 50A in someembodiments. For example, epitaxy region 50B may be epitaxially grown ona top surface of bottom substrate 50A. In some embodiments, epitaxyregion 50B may comprise germanium. For example, epitaxy region 50B maycomprise Si_(x)Ge_(1-x), where x can be between approximately 0 and 1.Epitaxy region 50B may be formed of a material that is different that amaterial that is used to form the bottom substrate 50A in someembodiments. For example, bottom substrate 50A may be free orsubstantially free of germanium in some embodiments.

The substrate 50 has a first region 100A and a second region 100B. Thefirst region 100A can be for forming n-type devices, such as NMOStransistors, such as n-type FinFETs. The second region 100B can be forforming p-type devices, such as PMOS transistors, such as p-typeFinFETs. The divider 15 between the first region 100A and the secondregion 100B indicates a physical separation between the first region100A and the second region 100B. Components of first region 100A may bephysically separated from components of second region 100B, but areillustrated side by side in FIGS. 2 through 24B for purposes ofillustration.

Although epitaxy region 50B is depicted as being formed in both region100A and region 100B, in some embodiments epitaxy region may only beformed on region 100A or region 100B.

FIG. 2 also shows the forming of mask 53 over substrate 50. In someembodiments, mask 53 may be used in a subsequent etching step to patternsubstrate 50 (See FIG. 3). As shown in FIG. 2, mask 53 may include firstmask layer 53A and second mask layer 53B. Mask layer 53A may be a hardmask layer, such as silicon nitride or the like, and may be formed usingany suitable process, such as a deposition, atomic layer deposition(ALD) or physical vapor deposition (PVD). Mask layer 53A may be used toprevent or minimize an etching of substrate 50 underlying mask layer 53Ain the subsequent etch step (See FIG. 3). Mask layer 53B may comprisephotoresist, and in some embodiments may be used to pattern mask layer53A for use in the subsequent etching step discussed above. Mask layer53B can be formed by using a spin-on technique and can be patternedusing acceptable photolithography techniques. In some embodiments, threeor more masks 53 may be used.

FIG. 3 illustrates the formation of semiconductor strips 52 in thesubstrate 50. First, mask layers 53A and 53B may be patterned, whereopenings in mask layers 53A and 53B expose areas of substrate 50 wheretrenches 55 will be formed. In some embodiments, the masks 53A and 53Bmay be patterned using a multiple-patterning process, such as aself-aligned double patterning (SADP) process, a self-aligned quadruplepatterning (SAQP) process, or the like, that allows for forming featureshaving a reduced critical dimension (CD) and pitch. In such embodiments,one or more additional mask layers, one or more mandrel layers, and oneor more spacer layers (not shown) may be formed over the mask 53. Theone or more additional mask layers, the one or more mandrel layers, andthe one or more spacer layers may be patterned to form desired patterns,which are transferred to the mask 53.

Next, an etching process may be performed, where the etching processcreates trenches 55 in substrate 50 through openings in mask 53.Trenches 55 may extend through epitaxy region 50B and partially throughbottom substrate 50A in some embodiments. The remaining sections ofsubstrate 50 underlying patterned mask 53 form a plurality ofsemiconductor strips 52. The etching may be any acceptable etch process,such as a reactive ion etch (RIE), neutral beam etch (NBE), the like, ora combination thereof. The etch may be anisotropic.

In FIG. 4 an insulation material is formed between neighboringsemiconductor strips 52 to form isolation regions 54. The insulationmaterial may be an oxide, such as silicon oxide, a nitride, the like, ora combination thereof, and may be formed by a high density plasmachemical vapor deposition (HDP-CVD), a flowable CVD (FCVD) (e.g., aCVD-based material deposition in a remote plasma system and post curingto make it convert to another material, such as an oxide), the like, ora combination thereof. Other insulation materials formed by anyacceptable process may be used.

Furthermore, in some embodiments, isolation regions 54 may include aconformal liner (not illustrated) formed on sidewalls and a bottomsurface of trenches 55 (see FIG. 3) prior to the filling of trenches 55with an insulation material of isolation regions 54. In someembodiments, the liner may comprise a semiconductor (e.g., silicon)nitride, a semiconductor (e.g., silicon) oxide, a thermal semiconductor(e.g., silicon) oxide, a semiconductor (e.g., silicon) oxynitride, apolymer dielectric, combinations thereof, and the like. The formation ofthe liner may include any suitable method, such as, ALD, CVD, highdensity plasma (HDP) CVD, PVD, and the like. In such embodiments, theliner may prevent (or at least reduce) the diffusion of semiconductormaterial from semiconductor strips 52 (e.g., Si and/or Ge) into thesurrounding isolation regions 54 during the annealing of isolationregions 54.

An anneal process may be performed once the insulation material isformed. In the illustrated embodiment, the insulation material issilicon oxide formed by a FCVD process. The insulating material may bereferred to as isolation regions 54. Further in FIG. 4, a planarizationprocess, such as a chemical mechanical polish (CMP), may remove anyexcess insulation material and form top surfaces of the isolationregions 54 and top surfaces of the semiconductor strips 52 that arecoplanar. In some embodiments, the CMP may also remove mask 53. In otherembodiments mask 53 may be removed using a wet cleaning process.

FIG. 5 illustrates the recessing of the isolation regions 54 to formShallow Trench Isolation (STI) regions 54. The isolation regions 54 arerecessed such that fins 56 in the first region 100A and in the secondregion 100B protrude from between neighboring isolation regions 54.Further, the top surfaces of the isolation regions 54 may have a flatsurface as illustrated, a convex surface, a concave surface (such asdishing), or a combination thereof. The top surfaces of the isolationregions 54 may be formed flat, convex, and/or concave by an appropriateetch. The isolation regions 54 may be recessed using an acceptableetching process, such as one that is selective to the material of theisolation regions 54. For example, a chemical oxide removal using aCERTAS® etch or an Applied Materials SICONI tool or dilute hydrofluoric(dHF) acid may be used.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 2 through 5 is just oneexample of how fins 56 may be formed. In other embodiments, a dielectriclayer can be formed over a top surface of the substrate 50; trenches canbe etched through the dielectric layer; homoepitaxial structures can beepitaxially grown in the trenches; and the dielectric layer can berecessed such that the homoepitaxial structures protrude from thedielectric layer to form fins. In still other embodiments,heteroepitaxial structures can be used for the fins. For example, thesemiconductor strips 52 in FIG. 4 can be recessed, and a materialdifferent from the semiconductor strips 52 may be epitaxially grown intheir place. In an even further embodiment, a dielectric layer can beformed over a top surface of the substrate 50; trenches can be etchedthrough the dielectric layer; heteroepitaxial structures can beepitaxially grown in the trenches using a material different from thesubstrate 50; and the dielectric layer can be recessed such that theheteroepitaxial structures protrude from the dielectric layer to formfins 56. In some embodiments where homoepitaxial or heteroepitaxialstructures are epitaxially grown, the grown materials may be in situdoped during growth, which may obviate prior and subsequentimplantations although in situ and implantation doping may be usedtogether. Still further, it may be advantageous to epitaxially grow amaterial in an NMOS region different from the material in a PMOS region.In various embodiments, the fins 56 may comprise silicon germanium(Si_(x)Ge_(1-x), where x can be between approximately 0 and 1), siliconcarbide, pure or substantially pure germanium, a III-V compoundsemiconductor, a II-VI compound semiconductor, or the like. For example,the available materials for forming III-V compound semiconductorinclude, but are not limited to, InAs, AlAs, GaAs, InP, GaN, InGaAs,InAlAs, GaSb, AlSb, AlP, GaP, and the like.

As will be described in detail below, in subsequent processing a dummydielectric and a dummy gate may be formed over fins 56 (see FIGS. 7A-Band 10A-C). In some embodiments, fins 56 may comprise certain ions thatdiffuse from fin 56 into the dummy gate dielectric and dummy gate. Forexample, if fins 56 comprise germanium, then the germanium in the fins56 may diffuse from fins 56 into the dummy gate dielectric and the dummygate. In some embodiments, germanium may diffuse until there is a highconcentration of germanium at an interface of the dummy dielectric andthe dummy gate. The high concentration of germanium at the interface ofthe dummy dielectric and the dummy gate may cause a degradation in thematerial of the dummy gate dielectric along the interface. During asubsequent removal of the dummy gate and the dummy dielectric to form areplacement gate and replacement gate dielectric, the degradation in thequality of the material of the dummy gate dielectric may createundesirable residue in the opening created by the removal of the dummygate and the dummy dielectric. The residue may prevent the replacementgate and/or replacement gate dielectric from being successfullydeposited, which may reduce performance of the device and/or may preventthe device from operating normally. The residue may decreasemanufacturing yield rates.

Referring to FIGS. 6A and 6B, a capping layer 51 may be formed over fins56. Capping layer 51 may help to reduce or prevent a diffusion of ions,e.g. germanium, from fins 56 into subsequently formed dummy dielectriclayer 58 (see FIGS. 7A and 7B) and subsequently formed dummy gates 70and 76 (see FIGS. 10A-C). Capping layer 51 may prevent or reduce theformation of the residue created during the removal of dummy gates 70and 76 and dummy dielectric 58 that is caused by the build up ofgermanium at the interface between the dummy dielectric 58 and the dummygates 70 and 76.

Capping layer 51 may be formed of any suitable material and using anymethod that is suitable for forming a capping layer over fins 65. Forexample, capping layer 51 may be formed using atomic layer deposition(ALD) or the like. In some embodiments, capping layer 51 may be formedof substantially pure silicon, and may be formed by epitaxially growinga layer of silicon over fins 56 or by a deposition process. In otherembodiments, capping layer 51 may be formed of SiON using a thermalnitridation and oxide deposition process. In other embodiments, cappinglayer 51 may be formed of Al₂O₃ using an ALD process. In otherembodiments, capping layer 51 may be formed of Si₃N₄ using an ALDprocess. Each of these embodiments is described in detail below.

In some embodiments, capping layer 51 may be formed of substantiallypure silicon. Capping layer 51 may be formed of substantially puresilicon using any suitable methods. In some embodiments, capping layer51 may be formed by epitaxially growing a layer of silicon over fins 56or by a deposition process, such as physical vapor deposition (PVD),plasma enhanced atomic layer deposition (ALD), or the like. Inembodiments in which capping layer 51 comprises substantially puresilicon, capping layer 51 may be formed using a process that isperformed at a temperature of about 500° C. or less. When capping layer15 is formed of substantially pure silicon, capping layer 51 may have athickness T1 in a range of about 10 Å to about 20 Å. A thickness T1 ofabout 10 Å or more may sufficiently prevent or reduce the diffusion ofgermanium from fins 56 into a subsequently formed dummy dielectricand/or dummy gate. A thickness T1 of about 20 Å or less may prevent orreduce a degradation of channel performance. For example, when cappinglayer 51 is formed over a high mobility channel, a thickness T1 above 20Å may reduce mobility of the channel such that the channel is no longera high mobility channel. Controlling thickness T1 to be about 20 Å orless may prevent the channel mobility from being unduly degraded.Forming a capping layer 51 of substantially pure silicon as describedherein may be suitable for fins 56 that have a concentration ofgermanium of about 25% or more.

In other embodiments, capping layer 51 may be formed using a thermalnitridation and oxide deposition process. In some embodiments, thethermal nitridation process is performed before the oxide depositionprocess. The thermal nitridation process may be performed at atemperature of about 600° C. to about 1000° C. and at pressures of about1 Torr to about 500 Torr. The oxide deposition may be performed usingALD, chemical vapor deposition (CVD), plasma-enhanced ALD, or the like.In some embodiments, SiO₂ may be deposited using plasma-enhanced ALD.For example, Bis(diethylamino)silane (BDEAS) may be used as a precursorgas, followed by the plasma-enhanced ALD process using C₈H₂₂N₂Si and O₂plasma to deposit SiO₂. A first reaction state may beSiH₂[N(C₂H₅)₂]₂+—OH→—O—SiH₂[N(C₂H₅)₂]+NH(C₂H₅)₂. A second reaction statemay be —O—SiH₂[N(C₂H₅)₂]+O*→—O—(Si—OH*)—O+H₂O+CO_(x)+other (N-containingspecies). The —O—(Si—OH*)—O of the second reaction state may createSiO₂. The plasma-enhanced ALD process may be performed at temperaturesat about 400° C. or less. The thermal nitridation and oxide depositionprocesses may create a layer of SiON having a thickness T1 of about 5 Åto about 15 Å, and a surface of the SiON may have a surface N atomicpercentage of about 2% to about 30%. Forming a capping layer 51 using athermal nitridation and oxide deposition process as described herein maybe suitable for fins 56 that have a concentration of germanium of about25% or more.

In other embodiments, capping layer 51 may be formed of Al₂O₃. Cappinglayer 51 may be formed of Al₂O₃ using any suitable method. In someembodiments, Al₂O₃ may be formed using an ALD process. For example,Trimethylaluminum (TMA) may be used as a precursor, followed by an ALDprocess using Al(CH₃)₃ with H₂O to deposit Al₂O₃. Al₂O₃ may be formedaccording to reaction A or B, where reaction A isAL-OH*+AL(CH₃)→AL-O-AL(CH₃)₂*+CH₄, and where reaction B isAL-CH₃*+H₂O→Al—OH*+CH₄. The AL-O-AL(CH₃)₂* may form Al₂O₃, andimpurities may be removed, for example during heating performed duringsubsequent processing. The ALD process may be performed at a temperatureof about 300° C. In some embodiments, the ALD process may be performedat a temperature of less than about 300° C. A thickness of capping layer51 may be determined at least in part in consideration of an operatingvoltage of the finFET device. For example, finFET devices having higheroperating voltages, such as input/output finFET devices for example, mayrequire a thicker gate dielectric, which in turn may require a thickercapping layer 51 at higher operating voltages than for lower operatingvoltages. For example, finFET devices may be configured to have voltagesof about 1.5V to about 2.0V applied to the gate electrodes to turn onthe finFET devices. When formed of Al₂O₃, and when fabricated forcircuits in which about 1.8V is applied to the gate electrode to turn onthe finFET device, capping layer 51 may have a thickness T1 of about 3 Åto about 47 Å. When formed of Al₂O₃, and when fabricated for circuits inwhich about 1.5V is applied to the gate electrode to turn on the finFETdevice, capping layer 51 may have a thickness T1 of about 3 Å to about42 Å. When formed of Al₂O₃, a thickness T1 of 3A or more may enable thecapping layer to prevent of reduce diffusion of germanium from fins 56into subsequently formed dummy dielectric layer 58 (see FIGS. 7A and 7B)and subsequently formed dummy gates 70 and 76 (see FIGS. 10A-C). Whenformed of Al₂O₃, a thickness T1 of 3A or more may prevent or reduce theformation of residue created during the removal of dummy gates 70 and 76and dummy dielectric 58 from a build up of germanium at the interfacebetween the dummy dielectric 58 and dummy gates 70 and 76.

In other embodiments, capping layer 51 may be formed of Si₃N₄. Anysuitable method of forming capping layer 51 of Si₃N₄ may be used. Forexample, capping layer may be formed by depositing Si₃N₄ using an ALDprocess. In some embodiments, dichlorosilane (DCS) may be used as aprecursor, followed by an ALD process using SiH₂Cl₂ and NH₃ to depositSi₃N₄. A reaction may include 3SiH₂Cl₂+4NH₃→Si₃N₄+6HCl+6H₂. The ALDprocess may be performed at a temperature of about 500° C. In someembodiments, the ALD process may be performed at a temperature of lessthan about 500° C. FinFET devices may be configured to have voltages ofabout 1.5V to about 2.0V applied to the gate electrodes to turn on thefinFET devices in accordance with some embodiments. For finFET devicesthat are formed to have 1.8V applied to the gate electrode to turn onthe finFET device, the capping layer comprising Si₃N₄ may have athickness T1 of about 20 Å to about 50 Å. For finFET devices that areformed to have 1.5V applied to the gate electrode to turn on the finFETdevice, the capping layer comprising Si₃N₄ may have a thickness T1 ofabout 20 Å to about 45 Å. When formed of Si₃N₄, a thickness T1 of 20A ormore may enable the capping layer to prevent or reduce diffusion ofgermanium from fins 56 into subsequently formed dummy dielectric layer58 (see FIGS. 7A and 7B) and subsequently formed dummy gates 70 and 76(see FIGS. 10A-C). Capping layer 51 may prevent or reduce the formationof residue created during the removal of dummy gates 70 and 76 and dummydielectric 58 from a build up of germanium at the interface between thedummy dielectric 58 and dummy gates 70 and 76.

In FIGS. 7A and 7B, a dummy dielectric layer 58 is optionally formed onthe capping layer 51. The dummy dielectric layer 58 may be, for example,silicon oxide, silicon nitride, a combination thereof, or the like, andmay be deposited (using, for example, CVD, PVD, or the like) orthermally grown (for example, using thermal oxidation or the like)according to acceptable techniques. According to some embodiments, thedummy dielectric layer 58 may comprise different materials than thecapping layer 51. FIGS. 7A and 7B depict an embodiment in which thedummy dielectric layer 58 does not extend over isolation regions 54. Insome embodiments, dummy dielectric layer 48 may extend over isolationregions 54.

As shown in FIGS. 7A and 7B, in some embodiments a dummy dielectriclayer 58 is formed on the capping layer 51. Dummy dielectric layer maysometimes be referred to as an interfacial layer. In other embodiments adummy dielectric layer 58 is not formed on the capping layer 51. Theneed for a dummy dielectric layer 58 may depend at least in part on thematerial composition of the capping layer 51 and an etch selectivity ofthe capping layer 51 with a material of a subsequently formed dummy gate70 and 76. For example, during subsequent processing a dummy gate 70 and76 will be formed (See FIGS. 10A-C) and subsequently removed (See FIGS.23A-B). During the removal of the dummy gates 70 and 76, an etch stoplayer is needed to determine a stopping point of the etching process. Ifcapping layer 51 has a good etch selectivity compared to a material ofthe dummy gates 70 and 76, then a separate dummy dielectric may not berequired. If the capping layer 51 does not have a good etch selectivelycompared to a material of the dummy gates 70 and 76, then dummydielectric 58 may be included and may act as the etch stop layer for theetch process.

In some embodiments, a thickness T2 of a combined thickness of thecapping layer 51 and the dummy dielectric layer 58, if present, may beconsidered. In embodiments in which capping layer 51 is formed ofsubstantially pure silicon, for finFET devices that are formed to have1.5V applied to the gate electrode to turn on the finFET device,thickness T2 may be from about 25 Å to about 45 Å. For finFET devicesthat are formed to have 1.8V applied to the gate electrode to turn onthe finFET device, thickness T2 may be from about 30 Å to about 50 Å.Substantially pure silicon may not have a good etch selectivity formaterials that are commonly used to form dummy gates. As such, whencapping layer 51 is formed of substantially pure silicon, dummydielectric layer 58 may be formed over capping layer 51 as shown inFIGS. 7A and 7B.

In embodiments in which capping layer 51 is formed of SiON created by athermal nitridation and oxide deposition process, for finFET devicesformed to have 1.5V applied to the gate electrode to turn on the finFEtdevice, thickness T2 may be from about 25 Å to about 45 Å. For finFETdevices formed to have 1.8V applied to the gate electrode to turn on thefinFET device, thickness T2 may be from about 30 Å to about 50 Å. SiONmay not have a good etch selectivity for materials that are commonlyused to form dummy gates. As such, when capping layer 51 is formed ofSiON, dummy dielectric layer 58 may be formed over capping layer 51 asshown in FIGS. 7A and 7B.

In embodiments in which capping layer 51 is formed of AL₂O₃, for finFETdevices formed to have 1.5V applied to the gate electrode to turn on thefinFET device, thickness T2 may be from about 25 Å to about 45 Å. ForfinFET devices formed to have 1.8V applied to the gate electrode to turnon the finFET device, thickness T2 may be from about 30 Å to about 50 Å.AL₂O₃ may have a good etch selectivity for materials that are commonlyused to form dummy gates. As such, when capping layer 51 is formed ofAL₂O₃, dummy dielectric layer 58 may be formed over capping layer 51 asshown in FIGS. 7A and 7B, or dummy dielectric layer 58 may not be formedin some embodiments.

In embodiments in which capping layer 51 is formed of Si₃N₄, for finFETdevices formed to have 1.5V applied to the gate electrode to turn on thefinFET device, thickness T2 may be from about 25 Å to about 45 Å. ForfinFET devices formed to have 1.8V applied to the gate electrode to turnon the finFET device, thickness T2 may be from about 30 Å to about 50 Å.Si₃N₄ may have a good etch selectivity for materials that are commonlyused to form dummy gates. As such, when capping layer 51 is formed ofSi₃N₄, dummy dielectric layer 58 may be formed over capping layer 51 asshown in FIGS. 7A and 7B, or dummy dielectric layer 58 may not be formedin some embodiments.

In FIGS. 8A and 8B, a dummy gate layer 60 is formed over the dummydielectric layer 58, and a mask layer 62 is formed over the dummy gatelayer 60. In embodiments in which dummy dielectric layer 58 is notformed, dummy gate layer 60 is formed directly over capping layer 51(See FIGS. 9A-B). The dummy gate layer 60 may be deposited over thedummy dielectric layer 58 and then planarized, such as by a CMP. Themask layer 62 may be deposited over the dummy gate layer 60. The dummygate layer 60 may be made of, for example, polysilicon, although othermaterials that have a high etching selectivity from the etching ofisolation regions 54 may also be used. The mask layer 62 may include,for example, silicon nitride or the like. In this example, a singledummy gate layer 60 and a single mask layer 62 are formed across thefirst region 100A and the second region 100B. In other embodiments,separate dummy gate layers may be formed in the first region 100A andthe second region 100B, and separate mask layers may be formed in thefirst region 100A and the second region 100B.

Referring to FIGS. 9A-B, as described above, in some embodiments dummydielectric layer 58 may be optionally omitted. In embodiments in whichdummy dielectric layer 58 is omitted, dummy gate layer 60 may be formeddirectly over capping layer 51.

In FIGS. 10A, 10B, and 10C, the mask layer 62 may be patterned usingacceptable photolithography and etching techniques to form mask 72 inthe first region 100A and mask 78 in the second region 100B. The patternof the masks 72 and 78 then may be transferred to the dummy gate layer60 by an acceptable etching technique to form dummy gates 70 in thefirst region 100A and dummy gates 76 in the second region 100B.Optionally, the pattern of masks 72 and 78 may similarly be transferredto dummy dielectric layer 58. The dummy gates 70 and 76 cover respectivechannel regions of the fins 56. The dummy gates 70 and 76 may also havea lengthwise direction substantially perpendicular to the lengthwisedirection of respective epitaxial fins.

Furthermore, although not explicitly illustrated, masks 72 and 78 mayfurther be used to pattern dummy gate layer 60 and optionally dummydielectric layer 58 in cross section A-A of FIGS. 1 and 10A.Specifically, the dummy gate layer 60 may be patterned to physicallyseparate dummy gates of adjacent finFET devices within each region 100Aand 100B. For example, dummy gates 70 and 76 may be physically separatedfrom each other as well as dummy gates of adjacent finFET devices (notexplicitly illustrated). In other embodiments, different masks (e.g.,other than masks 72 and 78) may be used to pattern the dummy gate layer60 in different cross sections (e.g., cross section A-A versus crosssection B-B of FIGS. 1, 10A, and 10B). A size of the dummy gates 70 and76, and a pitch between dummy gates 70 and 76, may depend on a region ofa die in which the dummy gates are formed. In some embodiments, dummygates 70 and 76 may have a larger size and a larger pitch when locatedin an input/output region of a die (e.g., where input/output circuity isdisposed) than when located in a logic region of a die (e.g., wherelogic circuity is disposed).

In FIGS. 10A-C, appropriate wells (not shown) may be formed in the fins56, semiconductor strips 52, and/or substrate 50. For example, a P wellmay be formed in the first region 100A, and an N well may be formed inthe second region 100B.

The different implant steps for the different regions 100A and 100B maybe achieved using a photoresist or other masks (not shown). For example,a photoresist is formed over the fins 56 and the isolation regions 54 inthe second region 100B. The photoresist is patterned to expose thesecond region 100B of the substrate 50, such as a PMOS region. Thephotoresist can be formed by using a spin-on technique and can bepatterned using acceptable photolithography techniques. Once thephotoresist is patterned, an n-type impurity implant is performed in thesecond region 100B, and the photoresist may act as a mask tosubstantially prevent n-type impurities from being implanted into thefirst region 100A, such as an NMOS region. The n-type impurities may bephosphorus, arsenic, or the like implanted in the first region to aconcentration of equal to or less than 10¹⁸ cm⁻³, such as in a rangefrom about 10¹⁷ cm⁻³ to about 10¹⁸ cm⁻³. After the implant, thephotoresist is removed, such as by an acceptable ashing process.

Following the implanting of the second region 100B, a photoresist isformed over the fins 56 and the isolation regions 54 in the secondregion 100B. The photoresist is patterned to expose the first region100A of the substrate 50, such as the NMOS region. The photoresist canbe formed by using a spin-on technique and can be patterned usingacceptable photolithography techniques. Once the photoresist ispatterned, a p-type impurity implant may be performed in the firstregion 100A, and the photoresist may act as a mask to substantiallyprevent p-type impurities from being implanted into the second region,such as the PMOS region. The p-type impurities may be boron, BF₂, or thelike implanted in the first region to a concentration of equal to orless than 10¹⁸ cm⁻³, such as in a range from about 10¹⁷ cm⁻³ to about10¹⁸ cm⁻³. After the implant, the photoresist may be removed, such as byan acceptable ashing process.

After the implants of the first region 100A and the second region 100B,an anneal may be performed to activate the p-type and n-type impuritiesthat were implanted. The implantations may form a p-well in the firstregion 50B, e.g., the NMOS region, and an n-well in the second region50C, e.g., the PMOS region. In some embodiments, the grown materials ofepitaxial fins may be in situ doped during growth, which may obviate theimplantations, although in situ and implantation doping may be usedtogether.

In FIGS. 11A, 11B, and 11C, a first gate spacer 80 is formed on exposedsurfaces of respective dummy gates 70 and 76 (FIGS. 8A and 8B) and/ordummy dielectric layer 58 over fins 56 (FIG. 8C). Any suitable methodsof forming gate spacers 80 may be used. In some embodiments, adeposition (such as CVD, ALD or the like) may be used form the firstgate spacer 80. In some embodiments, as shown in FIG. 8A, first gatespacer may have a thickness T3 of about 30 Å. First gate spacer 80 maycomprise any suitable material. In some embodiments, first gate spacermay comprise SiOCN.

In FIGS. 12A, 12B and 12C, implants for lightly doped source/drain (LDD)regions 75 and 79 may be performed. Similar to the implants discussedabove in FIGS. 7A, 7B and 7C, a mask (not shown), such as a photoresist,may be formed over the first region 100A, e.g., NMOS region, whileexposing the second region 100B, e.g., PMOS region, and p-typeimpurities may be implanted into the exposed fins 56 in the secondregion 100B to created LDD regions 79. The mask may then be removed.Subsequently, a mask (not shown), such as a photoresist, may be formedover the second region 100B while exposing the first region 100A, andn-type impurities may be implanted into the exposed fins 56 in the firstregion 100A to create LDD regions 75. The mask may then be removed. Then-type impurities may be the any of the n-type impurities previouslydiscussed, and the p-type impurities may be the any of the p-typeimpurities previously discussed. The LDD regions 75 and 79 may each havea concentration of impurities of from about 10¹⁵ cm⁻³ to about 10¹⁶cm⁻³. An anneal may be used to activate the implanted impurities.

Referring to FIGS. 13A-C, additional gate spacers may be formed overgate spacer 80. First, second gate spacer 83 may be formed over firstgate spacer 80. Any suitable methods of forming second gate spacer 83may be used. In some embodiments, a deposition (such as ALD, CVD, or thelike) may be used form second gate spacer 83. Any suitable material maybe used to form second gate spacer 83. In some embodiments, second gatespacer 83 may comprise SiOCN. As shown in FIG. 13A, in some embodimentssecond gate spacer 83 may have a thickness T4 of about 30 Å. Aftersecond gate spacer 83 is formed, third gate spacer 85 is formed oversecond gate spacers 83. Any suitable methods of forming third gatespacer 85 may be used. In some embodiments, a deposition (such as ALD,CVD, or the like) may be used form third gate spacers 85. Any suitablematerial may be used to form third gate spacer 85. In some embodiments,third gate spacer 85 may comprise SiN. Third gate spacer 85 may have athickness T5 of about 40 Å in some embodiments, as shown in FIG. 13A.More or less spacers may be used.

Next, a patterning process is performed to remove excess sections offirst gate spacer 80, second gate spacer 83 and third gate spacer 85.Any acceptable patterning process may be used. In some embodiments aphotoresist may be deposited (not shown) and patterned using acceptablelithograph techniques, where openings in the photo resist exposesections of first gate spacer 80, second gate spacer 83 and third gatespacer 85 to be removed. An etching process may be performed using thephotoresist as a mask. The etching process may be anisotropic. After theetching, sections of first gate spacer 80, second gate spacer 83 andthird gate spacer 85 over LDD regions and over isolation regions 54 maybe removed. The resulting structure is depicted in FIGS. 14A-C.

FIGS. 15A-C through 20 depict the formation of epitaxial source/drainregions 82 and 84 in first region 100A and second region 100B. In someembodiments, epitaxial source/drain regions 82 in first region 100A maybe formed before epitaxial source/drain regions 84 are formed in secondregion 100B. It is also possible to form epitaxial source/drain regions84 in second region 100B before forming epitaxial source/drain regions82 in first region 100A.

FIGS. 15A-C through 17 depict the formation of an epitaxial source/drainregion in first region 100A. During the formation of the epitaxialsource/drain region in first region 100A, e.g., the NMOS region, thesecond region 100B, e.g., the PMOS region may be masked (not shown).

Referring to FIGS. 15A-C, source/drain regions of the fins 56 in thefirst region 100A are etched to form recesses. The etching may beperformed in a manner that a recess is formed between neighboring dummygates 70. Any acceptable etching process may be used, and may includeone or more etching processes.

Next, as shown in FIGS. 16A-C, epitaxial source/drain regions 82 in thefirst region 100A are epitaxially grown in the recesses. The epitaxialsource/drain regions 82 may include any acceptable material, such as anymaterial that is appropriate for n-type FinFETs. For example, if the fin56 comprises silicon, the epitaxial source/drain regions 82 may includesilicon, SiC, SiCP, SiP, or the like. The epitaxial source/drain regions82 may have surfaces raised from respective surfaces of the fins 56 andmay have facets. Epitaxial source/drain regions 82 are formed in thefins 56 such that each dummy gate 70 is disposed between respectiveneighboring pairs of the epitaxial source/drain regions 82 (as depictedin FIG. 14B). In some embodiments the epitaxial source/drain regions 82may extend past fins 56 and into the semiconductor strips 52.

The epitaxial source/drain regions 82 in the first region 100A may beimplanted with dopants to form source/drain regions, similar to theprocess previously discussed for forming lightly doped source/drainregions, followed by an anneal. The source/drain regions 82 may have animpurity concentration of in a range from about 10¹⁹ cm⁻³ to about 10²¹cm⁻³. The n-type impurities for source/drain regions in the first region100A, e.g., the NMOS region, may be any of the n-type impuritiespreviously discussed. In other embodiments, the epitaxial source/drainregions 82 may be in situ doped during growth.

FIGS. 16A-C depict embodiments of epitaxial source/drain regions 82 inwhich each source/drain region 82 is physically separate from othersource/drain regions 82. In some embodiments, two or more adjacentsource/drain regions 82 may be merged. An embodiment of a finFET havingmerged source/drain regions is depicted in FIG. 17, which is taken alongthe C-C cross-section of FIG. 1. In FIG. 17, two adjacent source/drainregions 82 are merged. In some embodiments, more than two adjacentsource/drain regions 82 may be merged.

FIGS. 18A-C through 20 depict the formation of epitaxial source/drainregions in second region 100B. During the formation of the epitaxialsource/drain region in second region 100B, e.g., the PMOS region, thefirst region 100A, e.g., the NMOS region may be masked (not shown).

Referring first to FIGS. 18A-C, source/drain regions of the epitaxialfins in the second region 100B are etched to form recesses. The etchingmay be performed in a manner that a recess is formed between neighboringdummy gates 76, as shown in FIG. 16B. Any acceptable etching process maybe used.

Next, epitaxial source/drain regions 84 in the second region 100B areepitaxially grown in the recesses, as shown in FIGS. 19A-C. Theepitaxial source/drain regions 84 may include any acceptable material,such as material that is appropriate for p-type FinFETs. For example, ifthe fin 56 comprises silicon, the epitaxial source/drain regions 84 maycomprise SiGe, SiGeB, Ge, GeSn, or the like. The epitaxial source/drainregions 84 may have surfaces raised from respective surfaces of the fins56 and may have facets. In the second region 100B, epitaxialsource/drain regions 84 are formed in the fins 56 such that each dummygate 70 is disposed between respective neighboring pairs of theepitaxial source/drain regions 84. In some embodiments epitaxialsource/drain regions 84 may extend may extend past fins 56 and into thesemiconductor strips 52.

The epitaxial source/drain regions 84 in the second region 100B may beimplanted with dopants to form source/drain regions, similar to theprocess previously discussed for forming lightly doped source/drainregions, followed by an anneal. The source/drain regions may have animpurity concentration of in a range from about 10¹⁹ cm⁻³ to about 10²¹cm⁻³. The p-type impurities for source/drain regions in the secondregion 50C, e.g., the PMOS region, may be any of the p-type impuritiespreviously discussed. In other embodiments, the epitaxial source/drainregions 84 may be in situ doped during growth.

FIGS. 19A-C depicts embodiments of epitaxial source/drain regions 84 inwhich each source/drain region 84 is physically separate from othersource/drain regions 84. In some embodiments, two or more adjacentsource/drain regions 84 may be merged. An embodiment of a finFET havingmerged source/drain regions 84 is depicted in FIG. 20, which is takenalong the C-C cross-section of FIG. 1. In FIG. 20, two adjacentsource/drain regions 84 are merged. In some embodiments, more than twoadjacent source/drain regions 84 may be merged.

In FIGS. 21A-B, an etch stop layer 87 and an intermediate layerdielectric (ILD) 88 are deposited over the structure illustrated inFIGS. 15A-C through 20. In an embodiment, the ILD 88 is a flowable filmformed by a flowable CVD. In some embodiments, the ILD 88 is formed of adielectric material such as Phospho-Silicate Glass (PSG), Boro-SilicateGlass (BSG), Boron-Doped Phospho-Silicate Glass (BPSG), undoped SilicateGlass (USG), or the like, and may be deposited by any suitable method,such as CVD, or PECVD.

In FIGS. 22A-B, a planarization process, such as a CMP, may be performedto level the top surface of ILD 88 with the top surfaces of the dummygates 70 and 76. After the planarization process, top surfaces of thedummy gates 70 and 76 are exposed through the ILD 88. In someembodiments, the CMP may remove the masks 72 and 78, or portionsthereof. In other embodiments, masks 72 and 78 may be removed before ILD88 is deposited.

In FIGS. 23A-B, remaining portions of masks 72 and 78 and the dummygates 70 and 76 are removed in an etching step(s), so that recesses 90are formed. Each recess 90 exposes a channel region of a respective fin56. Each channel region is disposed between neighboring pairs ofepitaxial source/drain regions 82 and 84. During the removal, the dummydielectric layer 58 may be used as an etch stop layer when the dummygates 70 and 76 are etched. In embodiments in which dummy dielectriclayer 58 is optionally not included, capping layer 51 may be used as anetch stop layer when the dummy gates 70 and 76 are etched. The dummydielectric layer 58 and the capping layer 51, or just the capping layer51 if dummy dielectric layer 58 is not included, may then be removedafter the removal of the dummy gates 70 and 76. The resulting structureis shown in FIGS. 23A-B.

As discussed earlier, the capping layer 51 may prevent or reduce thediffusion of germanium or other ions from fins 56 into the dummydielectric layer and the dummy gate, and therefore may prevent or reducea buildup of a high concentration of germanium at the interface of thedummy dielectric layer 58 and the dummy gates 70 and 76. As such, afterthe removal of dummy gates 70 and 76 using the etching process, theresidue that would have been created by the buildup of a highconcentration of germanium at the interface of the dummy dielectriclayer 58 and the dummy gates 70 and 76 may be reduced or prevented.

In FIGS. 24A-B, gate dielectric layers 92 and 96 and gate electrodes 94and 98 are formed for replacement gates. Gate dielectric layers 92 and96 are deposited conformally in recesses 90, such as on the top surfacesand the sidewalls of the fins 56 and on sidewalls of the gate spacers86, and on a top surface of the ILD 88 (not explicitly shown in FIGS.24A-B). In accordance with some embodiments, gate dielectric layers 92and 96 comprise silicon oxide, silicon nitride, or multilayers thereof.In other embodiments, gate dielectric layers 92 and 96 include a high-kdielectric material, and in these embodiments, gate dielectric layers 92and 96 may have a k value greater than about 7.0, and may include ametal oxide or a silicate of Hf, Al, Zr, La, Mg, Ba, T1, Pb, andcombinations thereof. The formation methods of gate dielectric layers 92and 96 may include Molecular-Beam Deposition (MBD), Atomic LayerDeposition (ALD), PECVD, and the like.

Next, gate electrodes 94 and 98 are deposited over gate dielectriclayers 92 and 96, respectively, and fill the remaining portions of therecesses 90. Gate electrodes 94 and 98 may be made of a metal-containingmaterial such as TiN, TaN, TaC, Co, Ru, Al, combinations thereof, ormulti-layers thereof. After the filling of gate electrodes 94 and 98, instep 228, a planarization process, such as a CMP, may be performed toremove the excess portions of gate dielectric layers 92 and 96 and thematerial of gate electrodes 94 and 98, which excess portions are overthe top surface of ILD 88. The resulting remaining portions of materialof gate electrodes 94 and 98 and gate dielectric layers 92 and 96 thusform replacement gates of the resulting FinFETs.

The formation of the gate dielectric layers 92 and 96 may occursimultaneously such that the gate dielectric layers 92 and 96 are madeof the same materials, and the formation of the gate electrodes 94 and98 may occur simultaneously such that the gate electrodes 94 and 98 aremade of the same materials. However, in other embodiments, the gatedielectric layers 92 and 96 may be formed by distinct processes, suchthat the gate dielectric layers 92 and 96 may be made of differentmaterials, and the gate electrodes 94 and 98 may be formed by distinctprocesses, such that the gate electrodes 94 and 98 may be made ofdifferent materials. Various masking steps may be used to mask andexpose appropriate regions when using distinct processes.

Furthermore, gate electrode 94 and gate dielectric layer 92 may bephysically separated from gate stacks of adjacent finFET devices inregion 100A (see e.g., FIG. 26). Similarly, gate electrode 98 and gatedielectric layer 96 may be physically separated from gate stacks ofadjacent finFET devices in region 100B (see e.g., FIG. 27). In someembodiments, gate electrodes 94/98 and gate dielectric layers 92/96 maybe formed to have a same pattern as dummy gate stacks 70/76 (see FIG.7A). In such embodiments, gate electrodes 94/98 and gate dielectriclayers 92/96 may be physically separated from adjacent gate stacksbecause dummy gate stacks 70/76 were previously patterned to bephysically separated from adjacent dummy gate stacks as discussed abovewith respect to FIG. 10A. In other embodiments, a combination ofphotolithography and etching may be employed to pattern gate electrodes94/98 and gate dielectric layers 92/96 after deposition.

In FIGS. 25A-B, an ILD 100 is deposited over ILD 88. Further illustratedin FIGS. 23A-C, contacts 102 and 104 are formed through ILD 100 and ILD88 and contacts 106 and 108 are formed through ILD 100. In anembodiment, the ILD 100 is a flowable film formed by a flowable CVDmethod. In some embodiments, the ILD 100 is formed of a dielectricmaterial such as PSG, BSG, BPSG, USG, or the like, and may be depositedby any suitable method, such as CVD and PECVD. Openings for contacts 102and 104 are formed through the ILDs 88 and 100. Openings for contacts106 and 108 are formed through the ILD 100. These openings may all beformed simultaneously in a same process, or in separate processes. Theopenings may be formed using acceptable photolithography and etchingtechniques. A liner, such as a diffusion barrier layer, an adhesionlayer, or the like, and a conductive material are formed in theopenings. The liner may include titanium, titanium nitride, tantalum,tantalum nitride, or the like. The conductive material may be copper, acopper alloy, silver, gold, tungsten, aluminum, nickel, or the like. Aplanarization process, such as a CMP, may be performed to remove excessmaterial from a surface of the ILD 100. The remaining liner andconductive material form contacts 102 and 104 in the openings. An annealprocess may be performed to form a silicide at the interface between theepitaxial source/drain regions 82 and 84 and the contacts 102 and 104,respectively. Contacts 102 are physically and electrically coupled tothe epitaxial source/drain regions 82, contacts 104 are physically andelectrically coupled to the epitaxial source/drain regions 84, contact106 is physically and electrically coupled to the gate electrode 94, andcontact 108 is physically and electrically coupled to the gate electrode98.

While contacts 102 and 104 are depicted in FIG. 23B in a samecross-section as contacts 106 and 108, this depiction is for purposes ofillustration and in some embodiments contacts 102, 104 are disposed indifferent cross-sections from contacts 106 and 108.

As discussed herein, when fins of a finFET device comprise certain ions,e.g. germanium, the ions may diffuse from the fins into a dummydielectric and a dummy gate that are subsequently formed over the fins.In subsequent processing a dummy dielectric and a dummy gate may beformed over fins 56 (see FIGS. 7A-B and 10A-C). For example, if fins 56comprise germanium, then the germanium in the fins 56 may diffuse fromfins 56 into the dummy gate dielectric and the dummy gate. In someembodiments, germanium may diffuse until there is a high concentrationof germanium at an interface of the dummy dielectric and the dummy gate.The high concentration of germanium at the interface of the dummydielectric and the dummy gate may cause a degradation in the material ofthe dummy gate dielectric along the interface. During a subsequentremoval of the dummy gate and the dummy dielectric to form a replacementgate and replacement gate dielectric, the degradation in the quality ofthe material of the dummy gate dielectric may create undesirable residuein the opening created by the removal of the dummy gate and the dummydielectric.

A method is provided in accordance with some embodiments. The methodincludes forming a capping layer over a fin of a fin field effecttransistor (finFET), where the fin is formed of a material comprisinggermanium. The method also includes forming a dummy dielectric layerover the capping layer. The method also includes forming a dummy gateover the dummy dielectric layer. The method also includes removing thedummy gate, where after the removing of the dummy gate the fin isexposed through an opening in the dummy dielectric layer and the cappinglayer. The method also includes forming a replacement gate, thereplacement gate contacting the fin through the opening in the dummydielectric layer and the capping layer.

A method is provided in accordance with some embodiments. The methodincludes epitaxially growing a layer over a substrate, the layer beingformed of a material comprising silicon and germanium. The method alsoincludes patterning the layer and the substrate to form a fin of a finfield effect transistor (finFET), the layer being disposed in a channelregion of the fin. The method also includes forming a capping layer overthe fin, where the capping layer comprises Si₃N₄ or Al₂O₃. The methodalso includes forming a dummy gate over and contacting the cappinglayer. The method also includes removing the dummy gate using thecapping layer as an etch stop layer.

A structure is provided in accordance with some embodiments. Thestructure includes a fin formed in a substrate, where the fin comprisesa channel region comprising germanium. The structure also includes agate stack over the fin, wherein the gate stack contacts the fin throughan opening in a capping layer over the fin and an opening in a dummydielectric layer over the capping layer, where the dummy dielectriclayer is made of a different material than the capping layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A structure, comprising: a fin formed in asubstrate, wherein the fin comprises a channel region, the channelregion comprising germanium; a gate stack over the fin, wherein the gatestack contacts the fin through a capping layer over the fin and a dummydielectric layer over the capping layer, wherein the dummy dielectriclayer is made of a different material than the capping layer; and anelectrical contact over the gate stack.
 2. The structure according toclaim 1, wherein the capping layer comprises substantially pure silicon,SiON, Al₂O₃, or Si₃N₄.
 3. The structure according to claim 2, whereinthe capping layer comprises substantially pure silicon, the electricalcontact is configured to apply a voltage of 1.5V to the gate stack, andwherein a combined thickness of the capping layer and the dummydielectric layer is about 25 Å to about 45 Å.
 4. The structure accordingto claim 2, wherein the capping layer comprises substantially puresilicon, the electrical contact is configured to apply a voltage of 1.8Vto the gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 30 Å to about 50 Å.
 5. Thestructure according to claim 2, wherein the capping layer comprisesSiON, the electrical contact is configured to apply a voltage of 1.5V tothe gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 25 Å to about 45 Å.
 6. Thestructure according to claim 2, wherein the capping layer comprisesSiON, the electrical contact is configured to apply a voltage of 1.8V tothe gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 30 Å to about 50 Å.
 7. Thestructure according to claim 2, wherein the capping layer comprisesAl₂O₃, the electrical contact is configured to apply a voltage of 1.5Vto the gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 25 Å to about 45 Å.
 8. Thestructure according to claim 2, wherein the capping layer comprisesAl₂O₃, the electrical contact is configured to apply a voltage of 1.8Vto the gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 30 Å to about 50 Å.
 9. Thestructure according to claim 2, wherein the capping layer comprisesSi₃N₄, the electrical contact is configured to apply a voltage of 1.5Vto the gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 25 Å to about 45 Å.
 10. Thestructure according to claim 2, wherein the capping layer comprisesSi₃N₄, the electrical contact is configured to apply a voltage of 1.8Vto the gate stack, and wherein a combined thickness of the capping layerand the dummy dielectric layer is about 30 Å to about 50 Å.
 11. Adevice, comprising: a substrate; a fin formed in the substrate, the fincomprising an epitaxy region, wherein the epitaxy region comprisesgermanium; a capping layer overlying the epitaxy region of the fin,wherein the capping layer comprises substantially pure silicon, SiON,Al₂O₃, or Si₃N₄; a dummy dielectric overlying the capping layer, whereina material composition of the dummy dielectric is different than amaterial composition of the capping layer; a gate dielectric layerextending through the capping layer and the dummy dielectric to contactthe epitaxy region of the fin; a gate electrode overlying the gatedielectric layer; a gate spacer adjacent the gate dielectric layer, thedummy dielectric and the capping layer being interposed between the finand the gate spacer; and an electrical connector contacting the gateelectrode.
 12. The device according to claim 11, wherein the cappinglayer comprises substantially pure silicon, a concentration of germaniumof the epitaxy region is 25% or more, and a thickness of the cappinglayer is in a range of about 10 Å to about 20 Å.
 13. The deviceaccording to claim 11, wherein the capping layer comprises SiON, aconcentration of germanium of the epitaxy region is 25% or more, and athickness of the capping layer is in a range of about 5 Å to about 15 Å.14. The device according to claim 13, wherein a surface nitrogenconcentration of the capping layer has an atomic percentage in a rangeof about 2% to about 30%.
 15. The device according to claim 11, whereinthe capping layer comprises Al₂O₃, the electrical connector isconfigured to apply a voltage of about 1.5V to the gate electrode, and athickness of the capping layer is in a range of about 3 Å to about 42 Å.16. The device according to claim 11, wherein the capping layercomprises Si₃N₄, the electrical connector is configured to apply avoltage of about 1.8V to the gate electrode, a concentration ofgermanium of the epitaxy region is 25% or more, and a thickness of thecapping layer is in a range of about 20 Å to about 50 Å.
 17. The deviceaccording to claim 11, wherein the capping layer comprises Si₃N₄, theelectrical connector is configured to apply a voltage of about 1.5V tothe gate electrode, and a thickness of the capping layer is in a rangeof about 20 Å to about 45 Å.
 18. A fin field effect transistor (finFET),comprising: a fin comprising an epitaxy region, wherein the epitaxyregion comprises a channel region, and wherein the channel region ismade of silicon germanium; a capping layer over the fin; a dummydielectric layer over the capping layer; a gate stack over the fin,wherein the gate stack contacts the fin through the capping layer andthrough the dummy dielectric layer, wherein the capping layer contactsthe gate stack, and wherein the dummy dielectric layer is made of adifferent material than the capping layer.
 19. The finFET according toclaim 18, wherein a germanium concentration of the silicon germanium isat least 25%.
 20. The finFET according to claim 18, wherein the cappinglayer comprises substantially pure silicon, SiON, Al₂O₃, or Si₃N₄.